Stabilized silver halide emulsions



Patented Ma. so, 1948 STABILIZED SILVER HALIDE EMULSIONS Fritz W. H. Mueller, Binghamton, N. Y., assignor to General Aniline & Film Corporation, New York, N. Y., a corporation of Delaware No Drawing. Application October 6, 1944, Serial No. 557,546

5 Claims. (01. 95-7) This inventionrelates to the improvement of photographic emulsions and more particularly to the incorporation of anti-fogging or stabilizing agents into silver halide emulsions.

A large number of substances have been described as being effective in preventing an increase in fog and thus stabilizing or controlling the keeping quality of photographic emulsions. Many of these stabilizers have definite limitations in their ability to produce desirable effects without producing unfavorable side reactions. Thus, some stabilizers desensitize or produce fog when added during the mixing or ripening, but exert favorable effects when added to the melted emulsion before coating. It is one object of this invention, therefore, to produce a stabilizing emulsion of improved photographic quality while incorporating the stabilizing agents over a wider range of application during the manufacture of photographic emulsions.

In U. S. Patent 2,057,764 there is described a process of stabilizing photographic silver halide emulsions by incorporating sulfinic or .seleninic acids or their salts into the emulsion in the form of a solution in a suitable solvent during the preparation of the emulsion or by incorporating the stabilizer into the finished emulsion by bathing the emulsion layer with a weak solution of the stabilizer. It was found that the fogging influence of supports, preparation layers, backing layers, intermediate layers, sublayers, protective layers, or baryta layers could be prevented by incorporating these stabilizers into such layers. As compared with films which were not provided with the sulfinic acid or seleninic acid stabilizers, it is stated that the films containing the stabilizer showed areduction in fog density of approximately 50%. It has now been discovered that the stabilizing effect of the sulfinic or the seleninic acids or their salts, disclosed in U. S. Patent 2,057,764 can be considerably improved and the range of application greatly extended if small amounts of cystine or certain substituted cystine compounds are present in the emulsions containingthe sulfinates orseleninates Compounds of this type may have the formulae:

cH-N Z R=H or alkyl R1=H or acetyl, benzoyl, brompropionyl, chloroacetyl, carbaminyl, phenylacetyl, a-amino propionyl, carbo-benzoxy, benzo-sulfonyl, gu-

R represents =OHO or substituted benzylidene.

;Thus,-the photographic effect of sodium sulfinate or seleninate is improved bythe addition of 0.00025-0.0050 mols. per. mol of sulfinate or seleninate of such cystine or cystine derivatives as Group I:

Cystine Dicarbobenzoxy-cystine Di-N benzyl-dibenzenesulfonyl cystine Diguanyl cystine (=diguanidine dithio dilactylic acid) Di-glycyl-cystine Dichloroacetyl cystine Group II:- Dibenzylidene cystine (barium alt) Group III:

The improved result, expressing fog in terms or density units, is manifested in a reduction of the fog density of approximately two-thirds of the fog density obtained when using a sulfinate or seleninate alone. This reduction in fog density produces better clearness, better keeping quality and an unusual brilliance which is especially desirable radiographs. These improved 7 stabilizing or antifogging elfects of I cystine -J compounds yvh'en used with the sulfin'ate' or seleni'natestabili'zers were particularly surprising in view of the wellknown strong desensitizing action of cystine 'in--1-0 photographic emulsions, l

The same reduction in fog density is whether the cystine or subls't'itiite 'd -c'ysti'n 3 pound is added with the sulfinate orslenin tanned V m? ate during mixing or during the ripening' stage 'inthe process of making the silver-:halidaemu-lsion or to the molten emulsion prior to coating. the latter case, solvents for the stabilizer mixture are employed which do not affect emulsions such as water or organic solvents which are misin medical and industrial 5 Example II To -l' lilogram ofa gelatin-silver-halide emulsion containing fromfi to 7% of silver halide and approximately 8'%g gelatin there were added duriving thezrripenings stage at a pH of approximately If 153cc of a 20% solution of sodium benzene seleninate, and "3"cc. ofa solution of l-eystine phenyl hydantoin (1.7 gram dissolved in lliter of 75% methyl amen base and cut intotest-film=lengths-:Additional layers, intermediate layers, sublayers, protective similar test fi-lms'weremad'e-wit-h-the same silver layers, and baryta layers in? order to prevent the fogging influence of such-layers.

Without in any way/wishing to be bound by or limited to any-particular theory as to the mechanism of the f'additional stabilizing effect produced by the cystine or substituted cystine, it is believed that thisadditional'? stabilizing effect is either a catalyticone or is'due to a chemical interaction betweenithe cystine compound and halide emulsion-to which=hadzabeen addediiduring ripenin ":thesame-zquantity ii-ofe the. sodium ben- .zene selem'na-teras above but omittingrthe l-cys- -tineaphenyl-hydantoin;

"The i'ogrden'sity ofreach of these typ'est'of test .filnrwasiidetermined'forthefreshly 'preparedlilm ands-test :rpieces Pof eacha type were then'sincubated for a period of six -days atriC. It wasiobserved t-liatitthei fog density of I thea 'films 1" treatd with t 1 t 1 t t th possible pror3 benzenerseleninic acid towhich had=b"een added compounds depends tosfbriie extent on the pH +4 of the emulsion. Certain-'cystine derivatives were found preferable in acid emulsion, others gave optimum resultsin ammonia type emulsions. It also was found to be preferable in activating soluilz'qygtinel was -:reduced by about-67% inithecase of'? freslily prepared film iand"'%":after incubatibn I of the: fog-"rdensity of :ther films "whichehad ibeentreate'd with benzene seleninic'iacid alene.

; tEmampleiIi i fire. a gelatin'silver halide emulsion attain in 's ilvenhali de corresponding c0110 0. giof silver nitratej there were added after .prec'ipitatiori of the st nW d e z sulfinate to a braces 45 silver'halidea'nd prior tdthefirstdigestion:

of cystine derivatives t the i'sbluti'on t'an ne'at it for 30- minutes at 50. .C. iTlie renewing examplestwill serve to furtherillustrate :theinvention, it .being understood that the invention "is f' not ;.l-imited.- thereto "Example I v i' f ra of a; afi -s ee m i l- Ofitaining from"6tdf7% of silver halide and 'cc.' of -a 20%-solution of *sodi um'benz'ene sul- 20coxoffasolution consisting ofil g. of-a dig uaiiyl cystine in 5 cc. of 1/N=sodi-um hydroxide madeup in L liter of water.,

The pH of the emulsion-was'approximatelyrfifi. The'emulsion was washed ran'df after-'ripenediin iapizjifciiiin ateiy8%;"gelatinthere'were attided dui' F the usual manner. Samples': of this :emulsion ing the ripening stage ata pl-l"of "approximately "were compared ior clear-ness and"keeping quality 15 cc. of a 20% solution of sodium benzene 'sulfinate, and

' carbonate) The melted emulsion was-:eastpn-aifilm base and cut into test film lengths'eSim-ilantest films,

with samples-'ofanemulsion prepared, in the same ""manner but omitting the-u-diguanyl: cystinesolution. It was found that the emulsion containing "the cystinei'derivative was"considerablyimproved.

' EwamplaIV 'ro i kiiogiam of a {gelatin silver lialideeinul- "sio'n containing 6 to "7 ef silver"iialide arid 8% wafer-made" with thezsamev silver-halide? emulsion :efitinitherewas: a -3 l 'g {final but omitting the addition of the sodiumrbenzene sulfinate. Additional'similartest-filmswermade with the same silver-halide:emulsionr-to"which had been added during ripening-ithe sameifquantity of the sodiumbenz'enei-sulfinate' as above" but omittingrthe? lec'ystine.

The fo g density oi each ,of theseltypes of test i in for. th?'ires'hlyiireparedfilm en bated 15 cc. of a 20% aqueous solution of. sodium ben-' zene sulfinate, and I 2.5 cc. of a. solution consisting of 1 g. of the barium salt of dibenzylidenecystine in 1 liter of water,

This emulsionwas comparedwith an emulsion made in the same manner but omitting the dibenzylidene cystinesand found to be considerably I assestanner-i improved in its clearness and keepin qualities.

Example V A stabilizing solution was made up as follows:

mg. of diguanyl cystine anhydride dissolved in a small amount of methyl alcohol was added to 100 cc. of a aqueous solution of crystalline sodium benzene sulfinate.

The mixture was heated for thirty minutes at 50 C.

This solution was then used as a stabilizer by adding 15 cc. of the solution per kilogram of silver-halide-gelatin emulsion containing 6 to 7% silver halide and 8% gelatin during various stages of the making and ripening of the emulsion and as a coating final.

In all cases, it was found that the clearness of the emulsion was considerably improved as compared with a similar emulsion which did not contain the diguanyl cystine anhydride. Also it was found that the fog increased to a much less degree upon subsequent storage in the case of the emulsion of this example than if sodium benzene sulfinate was used without the cystine derivative.

Other cystine derivatives such as those specifically listed above can be substituted in equimolecular amounts for the diguanyl cystine anhydride of this example with similar results.

The improvement obtainable when the fog characteristic is expressed in density units will, of course, vary somewhat depending upon the type of gelatin and the formula used in making the gelatino-silver-halide emulsion. The following table which expresses average fog values based upon the tests referred to in the examples will serve to further illustrate the improvement which is achieved by using the cystine or substituted cystine compound in combination with the sulfinates or seleninates as additions to typical gelatin-silver-halide emulsions:

Fog of the Fog after Freshly 6 days Coated Incubation Type of Film Film at 50 C.

Density Units Film with the addition of sodium benzene seleninate or sulfinate as a coating finaL. 0. -0. 0. 250. Film with the addition of sodium benzene seleninate or sulfinate and cystine or cystine derivatives 012-0. 15 0. 15 019 Film made from emulsion to which had been added sodium seleninate or suliinate during ripening 0. 38-0. 45 0. 45-0. 55 Film made from emulsion to which had been added during the ripening sodium seleninate or sulfinate in combination with cystine or cystine derivatives. 0.12-0.15 0.15-0.19

What I claim as my invention and desire to be secured by Letters Patent of the United States is:

1. A photographic material comprising a, silver halide gelatin emulsion in contact with a member of the group consisting of a sulfinic acid, a seleninic acid and their salts, and a cystine compound selected from the group consisting of such compounds having the formulae:

CHr-SSCH:

a a HC--N/ H N/ R1 Bl OOH c0011 11. CH2SSC H1 rid-rain HC-N=Ra oon (30011 and I \Y/ wherein R stands for a member of the group consisting of hydrogen and alkyl; R1 stands for a member of the group consisting of hydrogen, acetyl, benzoyl, brom-propionyl, chloroacetyl, carbaminyl, phenylacetyl, m-amino propionyl, carbo-benzoxy, benzo-sulfonyl, and guanyl radicals; Rs stands for a member of the group consisting of benzylidene and substituted benzylidene radicals; and Y represents the atoms necessary to complete a heterocyclic ring system, in the proportion of from 0.00025 to 0.0050 mol of the member of the last named group to one mol of the member of the first named group.

2. A photographic material comprising a silver halide gelatin emulsion containing a member of the group consisting of a sulfinic acid, a seleninic acid and their salts, and a cystine compound selected from the group consisting of such compounds having the formulae:

wherein R stands for a member of the group consisting of hydrogen and alkyl; R1 stands for a member of the group consisting of hydrogen, acetyl, benzoyl, br-om-propionyl, chloroacetyl, carbaminyl, phenylacetyl, a-amino propionyl, carbo-benzoxy, benzo-sulfonyl, and guanyl radicals; R3 stands for a member of the group consisting of benzylidene and substituted benzylidene radicals; and Y represents the atoms necessary to complete a heterocyclic ring system, in the proportion of from 0.00025 to 0.0050 mol of the member of the last named group to one mol of the member of the first named group.

3. A photographic material comprising a silver halide gelatin emulsion in contact with a member of the group consisting of a sulfinic acid, a seleninic acid and their salts, and l-cystine in the proportion of from 0.00025 to 0.0050 mol of the l-cystine to one mol of the selected member of said group.

4. A photographic material comprising a silver halide gelatin emulsion in contact with a member of the group consisting of a sulfinic acid, a

seleninic acid and their salts, and a-diguanyl cystine in the proportion of from 0.00025 to 0.0050 mol of the a-diguanyl cystine to one mol' of the selected member of said group.

5. A photographic material comprising a silver halide gelatin emulsion in contact with a member of the group consisting of a sulfinic acid, a

seleninic acid and their salts, and dibenzylidene cystine in the proportion of from 0.00025 to 0.0050 mol of the dibenzylidene cystine to one mo] of the selected member of said group.

FRITZ W. H. MUEILER. (References on following page) REFERENCES CITED Number UNITE STATES PATENTS 5 Number Name V -Da.te

229 116 r nksm -xz n fi FOREIGN; PATENTS 1 ntry-:=::;: Date Y 

